1. Field
The invention is in the field of hollow archery arrow shafts and of mounting nocks to the rearward end of hollow archery arrow shafts.
2. State of the Art
Hollow archery arrow shafts are common and may be made of various materials such as aluminum, carbon, or a combination of aluminum and carbon. Aluminum archery arrow shafts generally are made of thin walled aluminum tubing cut to desired length. Aluminum-carbon shafts use such tubing as the support over which the carbon is placed. An arrow point is attached to the forward end of the shaft and a nock is attached to the rearward end of the shaft. The aluminum tubing used for archery arrow shafts comes in a variety of diameters which provide arrow shafts of various combinations of characteristics such as stiffness, weight, etc.
Traditionally, the rearward ends of the aluminum arrow shafts were swaged to a point and a plastic nock, having a tapered indentation to accept the swaged rearward point of the arrow shaft was glued to the rearward end of the shaft.
More recently with aluminum shafts, aluminum-carbon shafts, and with some carbon shafts, a standard size nock has been produced with a forwardly extending shank adapted for tight friction fit within a bushing secured in the rearward end of the arrow shaft. This allows the nock to be rotated for fine adjustment in alignment with the arrow fletching and allows relatively easy removal and replacement of a nock if it becomes damaged. Such an arrangement is shown in U.S. Pat. No. 5,067,731 to Bickel. Each different diameter arrow shaft requires a different bushing which fits into the selected shaft and provides a standard size bore therein to accept the standard size nock shank.
While a shank system such as shown by the Bickel patent provides the advantage of easy adjustability of the nock and replacement of the nock, and provides the advantage that a standard nock can be used on any diameter archery arrow shaft (the size of the bushing is different for each size shaft), a supply of different bushings is required for each different size shaft and the bushing adds extra weight to the rearward end of the arrow. Further, the bushing needs to be assembled into the arrow shaft which involves an extra step in arrow assembly.